This invention relates generally to inorganic membranes. Such membranes are particularly well suited for conducting chemical reactions including the mineralization of certain organic chemicals, the separation of mixtures and the treatment of municipal and industrial waste.
The use of membranes to separate mixtures and catalyze chemical reactions is becoming an important chemical technique. Membrane separations tend to require less energy than competing techniques such as distillations. Furthermore, the use of membranes in chemical processes can be less costly and more simple to implement than other techniques.
Many techniques have been employed to form inorganic membranes. Examples of these include laser drilling, slip casting, track etching, anodic oxidation and the use of sol gel technology. Sol gels are formed through the acid or basic catalysis of the hydrolysis of metal or semi-metal alkoxides. The gel can be dried and fired to yield amorphous and ceramic-type membrane materials. The use of sol gel technology to prepare titania ceramic membranes is described in PCT Patent No. WO 8900983 and WO 8900985, the contents of which are incorporated herein by reference.
Molecular sieve material has been used to effect separations and to catalyze chemical reactions. Molecular sieves are a class of materials which contain pores and/or cages with a size similar to that of many organic molecules. Accordingly, molecular sieves can differentiate and separate organic molecules based on the size of the molecules.
Semiconductor particles including metal oxides, sulfides and carbides have been used to catalyze many important reactions. These semiconductor materials have photoactivity and are well suited as catalysts in photochemical reactions. However, these reactions are typically conducted in a liquid suspension of the semiconductor particles.
Municipal and industrial waste management has become one of the most serious and urgent problems facing modern society. The most commonly employed solutions involve either land disposal or burning of organic waste material in either open air or closed system incinerators. However, these methods are becoming disfavored because of the limited availability of landfill sites and the high energy costs associated with incineration as well as the problem of dealing with the gases and solid incineration by-products.
Accordingly, it is desirable to produce improved membranes for carrying out important industrial processes. For example, it would be particularly desirable to develop membranes for treating municipal and industrial waste.